1. Field of the Invention
Embodiments of the present invention relate to a belt conveyance apparatus, an image forming apparatus, and an image forming system.
2. Description of the Related Art
In an apparatus which moves a belt by a driving roller, there is known a technology of controlling the belt surface speed based on detection of two sensors. One sensor of the two sensors detects the rotation speed of the driving roller, and another sensor detects the belt surface speed.
JP-A No. 2004-220006 discloses an image forming apparatus for controlling a belt speed by a secondary control loop which uses a second sensor to detect rotation speed of a driving roller, when a primary control loop which uses a first sensor to detect a belt surface speed is abnormal. When the primary control loop is abnormal because of dirt and there is expansion of the driving roller due to a rising temperature, the image forming apparatus is not controlled accurately. In this case the image forming apparatus needs to stop operation.